Traffic actuated control apparatus



Feb. 27, 1951 J. BARKER 2,542,978

TRAFFIC ACTUATED CONTROL APPARATUS Filed Aug. 16, 1949 4 Sheets-Sheet lFIG. I

OCC

ICC

RSC

JNVEN TOR. FIG. 2

JOHN L. BARKER ATTORNEY Feb. 27, 1951 J. L. BARKER TRAFFIC ACTUATEDCONTROL APPARATUS .4 Sheets-Sheet 2 Filed Aug. 16, 1949 INVENTOR.

JOHN L. BARKER QM (21M ATTORNEY Patented Feb. 27, 1951 UNITED STATESPATENT OFFICE TRAFFIC ACTUATED CONTROL APPARATUS John L. Barker,Norwalk, Conn., assignor to Eastern Industries, Incorporated, EastNorwalk, Conn., a corporation of Delaware Application August 16, 1949,Serial No. 110,559

' 19 Claims. 1

This invention relates to trafiic actuated control apparatus andmethods, and more particularly to apparatus for automatic selectionamong several coordinated trafiic signal timing patterns in response toa sampling of trafiic conditions by traffic actuation.

From one aspect the'invention relates to apparatus for selection amongtrafilc signal offset systems for one or the other of two trafficdirections or for both directions along a roadway in response to trafiicactuation by trafiic in the respective directions, as for exampleinbound and outbound trafiic directions.

From another aspect the invention relates to apparatus for selectionamong such offset systems in response to the relative positions of twocycle selectors, one for each traific direction, and each adapted toselect one of a scale of cycle positions in response to trafficactuation in its direction over a scale of trafiic volume per unit timeperiod.

From a further aspect the invention relates to apparatus for selectionof the higher of two cycle positions selected individually by twotraffic actuated cycle selectors from their respective similar scales ofcycle positions, one for each of two trainc directions, where differentcycle positions are selected by the two cycle selectors, and forselection of the same cycle position where corresponding cycle positionsare selected by the two cycle selectors.

Various types of systems are wellknown for coordination of trafficmovement through a series of traflic signals along a street or highway.Certain systems of this type provide for the crosstrafijc periods atsuccessive trafiic signals along the highway to come in at progressivelylater time periods in proceeding along the highway in a given directionfor exampleso that the green signal period available for the highwaytrafiic at the succession of intersections appears to travel along thehighway and thus permits fleets of cars to proceed at the designedspeed'of the system through the series of traflic signals with a minimumof stopping for accommodation of cross traflic. Such traffic signalcontrol systems are often referred to as progressive systems.

The time lag between any given common reference point in anyrepresentative traffic signal cycle in a progressive system and theappearance of the desired corresponding point in the cycle of anindividual traific signal in the system is often referred to as theoffset for that signal, and it is already well known to provide one setof ofisets for inbound traffic movement in the morning into the centerof a city for example, with another set of ofisets for the outboundtraffic movement which usually characterizes the heavy traffic flowperiods of the late afternoon. In addition a third set of offsets foraverage or best two-way progressive trafiic movement is often providedfor the periods of the day when it is anticipated that the traffic is.not predominantly in one direction.

One difiiculty in such systems however has been that the peak periods ofinbound and outbound traffic do not always occur at the same times oncorresponding days on week days or on week ends for example and variousweather conditions and the occurrence of public events attractingconsiderable amounts of trafiic will vary the traffic patterns from timeto time so that any means.

of setting up in advance a program of the selection of the properoffsets and traffic control cycles' for various times of day and variousdays of the week is unable to adjust for these irregular l variations.

It is also already known to provide apparatus for selection, by trafiicactuation at a suitable traflic sampling point, between difierent typesor lengths of traflic control cycles for the trailic signal system or toadjust the timing of the overall trafiic signal system step by step atshort time intervals to accommodate the actual traflicvariationsas theyoccur. Apparatus of this charactler is sometimes referred to as atraflic cycle selector and my Patent No. 2,288,601 dated July 7,1942 isdirected to such apparatus.

In one embodiment of the present invention selection between inboundofiset, outbound onset and average offset is made in accordance with therelative positions of two. cycle selectors, which may be of the formdisclosed in the Patent 2,288,601 referred to for example, as somewhatmodified as pointed .out hereinbelow. According to one aspect oftheinvention one cycle selector and an associated traflic actuated detectorunit are provided for inbound traflic at an appropriate "sampling pointon the highway common to the the two. ofisets.

3 apparatus and offset selector apparatus and associated apparatusserving as a master control system for supervising the operation of theindividual trafiic signal controllers at the individual signalizedintersections along the highway.

In some cases the preferred location of the cycle selector and offsetselector apparatus may be near the middle-of the series oftrafiicsignals along the highway and in other cases thepreferredlocation may be near one end of the series,

in accordance with the best traflic sampling conditions.

In the operation of the selector apparatusfrom its broader aspects theinbound. and outbound traflic streams are respectively ineffect;measured or counted over a time period and duringsuch time period theindividual cycle selectors remain on a given trafiic control time cyclefor master control of the various individual traffic signal controllers.Near the end of such traffic sampling time .periodthe individual cycleselectors de termine Whether toremain on thesamecycle or to change to. alonger cycle or to ashorter .cycle in. accordance with thetrafiic.counted,.for.example. If. the trafiic counted is. substantiallthe same as in the precedingsampling time period the. cycle selectorremains. on.the. same. cycle .but if the t'raiiicv hasv increasedsubstantially thecycle selector willselect. the next. higher or. longercycle in the series, or if the. trafiic. countlhas decreasedsubstantially the cycle selector will selectthenext lower or shortercycle. in. the series. for thenext sampling time period. At .the .endof. each samplingtime .periodthe counting of traffic is reset. andanother sampling time. period is started.

-Each.cycle selectorhas. a number ofdifferent cycles to. select from.The Batent 2,288,6D1re- .ierredto illustrates six. cycles or cyclepositions A to F for example although it is obvious that more. or. less,could be provided. if. desired,

presentv apparatus-provides a means .of selecting among. the. inboundand'outbound offset systems in.accor.dance.with the positions of theinbound andoutboundcycle selectors. ..For .example ifv theinbound andoutboundcycle selectors areboth. on the-same or corresponding. cycle.positions,..indicating substantially the. same traffic flow ineachdirection, theoffsetselector.apparatus in accordance with one. aspectof.thepresent invention would select the average. offset. Similarly. in.oneform of..the.. invention lithe inbound and outbound cycle. selectorsarenot, more than one cycle position apart the offset. selector willcontinueto select.the.average...offset. Ontheother hand if. forexampletheinbound. and outbound cycle. selectorsare two or more cycle positionsapart the offset. selector willselectthe higher .of

Thus. if theinbound .cycle. selector is, two. cyclepositionshigher..than the out- .bound cycle selectorthe. inbound offset .will beselected by the offset. selector, but. if the outbound-cycle selectoristwo: or more cycle positions higher than, theinbound. cycle selector theoutbound offsetwill be selectedv by thev ofisetselector.

As described later hereinthe offset selector can be adjustedto. switchto theproperinboundor outbound. olTset when the. cycle, selectors. are.one

cycle position apart if desired, or it. can bev adjusted to switch to.the proper inboundoroutboundoffsetwhen the cycle selectors are threeor.more: cycle-.positionsapart. if desired, .instead of thev two cycle.positionseparation adjustment, just described forexample.

During a large part of the day at most trafllc signal systems along astreet or highway there is no predominantly heavy trafiic in either onedirection along the highway and the average offset is in general bestsuited for such relatively balanced trafiic since it is designed toprovide best for traiiic movement in both directions through: the seriesof signals. In sampling traffic for. any relatively short time period itis obvious that there may be momentary or brief periods of increasedtraffic in one direction which are not truly representative of acontinuing condition orevenoi a trend toward such continuing con-.dition. .Under such circumstances it has been:found.desirableto-provide greater stability in the rsystempby requiringthe cycle selectors to be more .than one position apart before a changeto either inbound or outbound offset and this is the preferred' form ofthe invention.

It will also be appreciated that the general level of traffic willvaryconsiderably throughout the day andnight. andthat it may be desirable.under circumstances of .moderate traflic but predomi- .nantlyinboundtrafiicas .may occur in the early eveninghours. for exampletohave the system on an inbound ofiset butata total cycle length ofaverage or moderatelength somewhat between the longest and. theshortestcycles. Itwill beunderstoodi by those skilled in the-art. thatthe most desirablecycle. length is. related tothespeed and volumeoftraific through a series. of traflic sig- .nals, the cycle length beingapproximately inversely proportional to such speed .for best two- .way.progressive trafiic movement for example, and it will-alsobe understoodthat as the volume .of. trafiic increases the speed .of traffic tends todecrease and agreater cycle length is needed to .clearthe .trafiic. Thuslonger time cycles are better adapted. to care for the greater trafiicvolumes and the. lower speeds that ordinarily accompany such. greatertrafiic volumes.

Thus at. some. times it willbe desirable to. op-

.erate the signal .system on an inbound oiiset but on a relatively,longtime cycle and other times .on .aninbound offset at a moderate orshorter time cycle whileat stillother times it .Will bedesirabletooperatethe system. on an outboundoffset. for. longer orshorter timecycles.

Thus the presentapparatus according to the present invention is designedto provide. for selection of offsets. up and down the scale of a numberof. different cycle lengths so that whichever direction of vtrafiicispredominant will be the..con.trolling'factor and obtain a preferential.ofiset and. at thesametime. obtain an appropri- ..ate cycle length. Theapparatus is also designed .to. accommodate average or relativelybalanced traffic and to. provide. for theselection of.approvpriatecycle'. length and adjustment of. such cycle length inaccordance with'the actual demands of trafiic up. anddownthe. scale.even. if. the traific remainssufliciently balanced to required an average. oifset.

Therefore. it is. an object of the invention to provide apparatusandmethods for automatic selectionandadjustmentof cycle length andoffsettobestaccommodate the volume of traffic in opposite'directionsthrough. a series of traffic control. signals.

It is another object of the invention to select automatically amonginbound, outbound and average ofisets in response to sampling of in-..bound and outbound. trafiic.

It isa. further objectto select among appropri- .ate...tr.afiic.signaltiming systems for trafiic pridirections in response to predominanttraffic in the corresponding direction, and to bias such selection ofoffset by maintaining such preferential offset on less predominanttraffic than that required to change to such preferential offset.

It is a further object to select among preferen- I tial offsets for eachdirection and non-preferential offset for both directions along aroadway in accordance with the relative positions of two cycle selectorsfor the respective directions and each operated by trafiic actuation inits direc-- tion to assume one of a scale of positions corresponding toa scale of low to high time rate of traffic actuations.

It is a further object to provide automatic selection among preferentialoffsets for one direction or the opposite direction or anon-preferential offset for both directions, in response to predominanttrafho in one direction, or in the opposite direction, or substantiallybalanced trailic in both directions, respectively over a considerablerange of cycle lengths for the traflic signaling time cycle at a seriesof trafl'ic signals.

Other objects of the invention will appear from the accompanying claimsand from the following description of the invention with respect to fthe drawings in which:

Fig. 1 illustrates in schematic or block diagram form, a traffic controlsystem employing apparatus according to one embodiment of the invention.

Fig. 2 similarly illustrates a series of intersections along a highwaytogether with the individual traffic signals and associated controls andconnections with the master control apparatus of Fig. l.

Fig. 3 illustrates a circuit diagram for the off set selector andassociated apparatus in accordance with one preferred form of theinvention.

Fig. 4 illustrates a circuit diagram of the cycle selector timeremployed in'common for two associated cycle selectors.

Fig. 5 illustrates schematically one form of cycle generator which maybe employed for variable frequency power in the master controlapparatus.

Fig. 6 shows circuit diagrams and offset cam arrangements for two localcycle-offset units of the master control apparatus for controlling thecycle length and offset of two traffic signal controllers.

Fig. '5' illustrates a circuit diagram of one form of traffic signalcontroller which may be operated on a traflic actuated basis or on afixed time basis, under control of the master control apparatus.

Fig. 8 illustrates schematically the circuit diagram of a master controlunit for controlling the resynchronization circuit for the local controlunits.

Referring now to Fig. 1 in more detail a section may be a part of astreet or highway for example extending through a series ofintersections provided with traflic signals.

In one side of the roadway a trafiic actuatable detector unit DDI,indicated schematically as a pair of contacts, is located in the path oftraffic in one direction which will be referred to as the inboundtraflic direction for convenience of reference. In the other side of theroadway a similar detector unit D is located in the path of traffic inthe opposite direction which will be referred to as the outbound trafficdirection. These detector units may be of any well known type adapted toclose a pair of contacts upon passage of a vehicle thereover, forexample,

The apparatus schematically indicated in Fig. 1 represents in generalthe master control apparatus for a series of traffic signals andassociated individual controllers at the several intersections along thehighway HY. Several of such intersections are illustrated schematicallyin Fig. 2 for example, showing the traffic signals ITS, ZTS and 3T8 andassociated controllers lTC, 2TC and 3T0 respectively, with localcycle-offset units ILC, ZLC and 3LC.

Returning to Fig. l the master control appara tus includes for examplean inbound cycle selector designated I08 and an outbound cycle selectordesignated OCS, connected to the respective inbound and outbounddetectors EDI and DDO.

Instead of each cycle selector incorporating a separate timer forsetting up the traffic sam pling period as in my Patent 2,288,601previously mentioned, for the purpose of the present invention it ispreferable to employ a common timer to control the traffic sampling timeperiod for both of the cycle selectors ICE and OCS, and this commontimer is illustrated schematically by the block CST between these twocycle selectors and connected to them.

Below the two cycle selectors is a block designated OS illustrating theoffset selector apparatus which controls the proper output circuits ICC,OCC' shown at the right for providing the appropriate offset system forthe traffic signals in accordance with the relative positions of the.

two cycle selectors, as controlled by the inbound and outbound trafficdetectors.

Each of the cycle selectors ICS and 00S is illustrated as having sixoutput connections, corresponding to the six cycle positions A, B, C, D,E, F of the Patent 2,288,601 referred to, and in the present inventionthese six cycle position connections are illustrated. in Fig. 1 asextending into the block below designated OS for the offset selectorunit. In addition to these connections a seventh connection from each ofthe cycle selectors to the offset selector unit is illustrated which isin addition to those provided in the Patent 2,288,601 referred to, andis for the purpose of indicating to the offset selector when either ofthe two cycle selectors ICS or 008 is stepping down from a higher to alower cycle position, as for example from cycle E to cycle D, as will befurther explained in more detail below.

As will later be further explained the inbound cycle selector ICS willapply electric power on one of its cycle position output circuits of itsA to F cycle scale in accordance with the cycle it is selecting at themoment in response to its measurement of trafirc actuating the traflicdetector DDI. Correspondingly the outbound cycle selector OCS will applypower on one of its six cycle position circuits of its A to F cyclescale in accordance with the cycle it is selecting in response to itsmeasurement of traiiic actuating rascega'zs '7 the detectonDDO. Thusthese output circuits from the cycle selectors provideinput controlcircuits: to the: offset; selector'OS: according to which .the offset.selector provides power onits appropriate-output circuitsj.ICC,..OCC toprovide. selection-iof the appropriate ofiset forthe traiio-signalsystem;

Aswill also later be described the apparatus I can beapplied to atrafiic signal system in which the individual signals are. controlledentirely on a: timedbasis. from. the master controller so: that themaster controlleralone is controlled by the rtrsrificvactuation, andsuch'trafiic actuation may come only from the inboundand outboundtrailic detectors DDIrandDDO for example.

The. apparatus. may also be employed however in connection with atraffic signal system in which one or more of the individual trafiicsignals is controlled jointly by the master controller and. by localtrafiic actuation by means of one or .more traific detectors local tothe individual in tersections in accordance with one or another of*various well-known types of trafilc actuated traffic signal systems.

Trafficsignal systems of the first type are often referred to as fixedtime or pretiined traffic signal systems and those of the second typeare often referred to astrafiic actuated signal systems.

Particularly where the apparatus is applied to traffic actuated signalsystems the ofiset selector apparatus and its associated output circuitsare preferably arranged to provide a means of disconnecting theindividual trailic signal controllers from supervision of the mastercontrol under certain traflic conditions so that they can respondlocally without delay to the traflic actuation of the local trafficdetectors. Such operation becomes desirable for example in extremelylight traflic as may occur in the late night hours or occasionally atother times during the day. It will be appreciated that if the flow oftrafilc becomes so light that there is no particular traflic pattern andthere are only occasionai isolated carstraveling along the highway, withfrequent occurrence of several successive traffic signal cycles at thevarious intersections without any interruption of the highway'traffic'in absence of "cross trafiic and thus lack of cross-traffic actuation,it becomes unnecessary to provide'for any progressive flow of traflicthrough the series of intersections and consequently unnecessary toprovide any master control of the timing of the individual trafiicsignal controllers. It will also be appreciated'thatin event of failureof the,--'

master control apparatus alone it will be desirable to free theindividual traffic signal controllers from 'master control. This isaccomplished in one preferred aspect of the invention by releasing thelocal' traflic signal controllers from master controlby'disconnectingpower from both of the circuits ICC and OCC.

The master control time cycle for the different offsets and for thevarious traffic signal controllers may be providedentirely'fromthemaster control point by direct connection individual-lyto the severaltraffic si nal controllers or maybe provided by running the outputcircuits ICC-and OCC to the several intersections, and providingindividual local cycle and offset units between themaster control andthe local signal control but located at each local signal controller totime the proper master control time cycle for the individual localcontroller, under the supervision of the master controller.

'of the individual traiiic signal controllers can be 8 Various systems"-of; control. are well-known for this purpose. .For example. theindividual. local oifset and cycle :units may be operated by synchronousmotors so. as to operate eachsuch local unit instep with the mastercontrol, and such local unit may be resynchronized once per cycle withthe master control. Each such individual control: unit maybe operated ona long or short cycle-in accordance with long or short master controlcycles so that the total time cycle of all controlledby the mastercontrol, as will be more fully described below.

'Io the right of the offset selector 0S inli ig. 1 there is illustratedschematically a cycle generator unit CG which serves as a mastertimer'for control of the master time cycle for the several individualtraffic signal controller-s at the several intersections. This cyclegenerator CG is shown connected to six output circuits from the right ofthe offset selector ()3 corresponding to the scale of six cyclepositions A through F forexample. This cycle generator CG may be of themaster timer type illustrated in the Patent 2,288,- 601 for example,employing six timing motors for 'six time cycles of various length, ingeneral progressively longer over the scale of A to F for example, andproviding individual output-circuits to various individual intersectioncontrollers as disclosed in the Patent 2,288,601 mentioned. However thiscycle generator may alternatively provide an output of variablefrequency cycle power to operate individual synchronous motors in cyclecontrol timing units associated with or forming a part of the individualtrafilc signal controllers at the several intersections as indicated inFig. 2, and in such case may have the variable frequency power outputcircuit VCCl, VCC-Z as illustrated in Fig. l.

The output circuits ICC and OCC extending to the right from the offsetselector OS represent circuits which are individually actuated toprovide the inbound oilset control or outbound ofiset controlrespectively for the variousindividual controllers at the variousintersections for example. As will be described more fully below,

this arrangement permits t is choice of. four di ferent ofisets or cyclecontrol combinations by these two circuits ICC and OCC, b means of whichthe inbound oliset can be provided by actuation of ICC alone, theoutbound offset can be provided by actuation of OCC alone, an average ortwo-way offset can be provided by actuation of both circuits ICC and OCCtogether, and still another offset or means of releasing the individualintersection controllers from master control coordination to permit themto operate independently for emergency or extremely light traiiicconditions if desired, may be provided by absence of actuation of eitherof the circuits ICC If it is desired to provide individual offsetcircuits at the master control apparatus or in common for the severalintersections this can be done by the provision of a master cycle unitas indicated schematically by the block designated MCU at the lowerright of Fig. l. which has input circuits above, connecting with theoutput circuits ICC and CCC of the offset selector, and has outputcircuits below designated ICC, OOC, AOC, and PRC to indicateschematically the inbound offset, outbound offset, average offset andindependent or free operation circuit respectively previously mentioned.

'iThis'master cycle unit MCU is also connected by other input leadsshown at the top to the variable frequency power output circuit VCCI andVCCZ of the cycle generator CG, in order to operate the master cycleunit on longer or shorter cycles in accordance with lower or higherfrequency cycle power from the cycle generator. The master cycle unitMCU also provides preferably a resynchronizing circuit shown as circuitRSC extending from the right side of the master cycle unit. Thisresynchronizing circuit preferably extends to all of the individualcycle offset um'ts associated with the individual intersection signalcontrollers to assure prompt resynchronization in the event ofindividual controllers or cycle units getting temporarily out of step asa result of power failure or the like.

The circuits OCC, ICC and RS employ a ground return from the individualintersection control units in the form illustrated but may alternativelyemploy a common wire return if desired.

Referring now to Fig. 2, three intersections are shown as illustrativeof a series of intersections along the highway HY. Individual trafficsignals for the individual intersections are indicated schematically atITS, 2T8 and 3T8, and their associated controllers are indicated as ITC,ZTC and 3TC respectively. One or more of the controllers may be of thetr-afiic actuated type as indicated in the case of ITC for example whichis connected with detectors lDSl and IDSZ in the side road approaches tothe intersection. It will be appreciated that the controllers mayalternatively be of the so-called fixed time or nontraffic actuatedtype, which proceeds through its cycle automatically under control ofthemaster cycle control apparatus from receipt of the actuating releaseimpulses to start the individual controller from its rest position atthe proper offset depending upon which of the offset circuits isactuated by the offset selector apparatu in the master controlapparatus.

In similar manner the trafilc actuated controller will proceed throughits cycle of signal indications to accord right of way to the sidestreet and to the highway and come to rest normally with the right ofway accorded to the highway until a combination of two events occurs:first, the actuation of one of the side street trafiic detector andsecond, the receipt of the ermissive or release impulse at the properoffset in accordance with which of the offset circuits is actuated inthe master control apparatus One form of local trafiic signal controllerunder the control of a master control apparatus, is

shown more fully in Fig. '7 and described later in connection with thisfigure.

Referring now to Fig. 3 which shows the detailed circuit of the offsetselector unit, the highway l-IY and the trafiic sampling detectors DDIand DB0 for inbound and outbound traffic are shown schematically againat the top of this figure together with the schematic showing of theirassociated cycle selectors ICS and OCS and the common traffic samplingperiod timer CST.

Alternating current power supply wires are shown at the left and rightsides of Fig. 3, the A. C. power wire at the right being designated by aplus sign in a circle and the A. C. ground or return wire at the leftbeing designated by a minus sign in a circle. This plus or positive wirepreferably provides A. C. at normal supply service voltage with respectto the minus or negative wire at the left for convenience. However alower voltage A. C. supply with respect to the negative wire is alsopreferably provided in such case by the wire at the right designated LVin a circle for some connections as described below. Connections forpower supply to the cycle selectors ICS and OCS and to the timer CST areprovided via wire Hi to negative power at the left and via wire I I topositive power at the right.

The connections from the inbound and outbound cycle selectors ICS andOCS are made from their respective cycle position terminals to therespective input circuits of the ofiset selector below for the severalcycle positions. The output terminals of the inbound cycle selector ICSfor its several cycle positions are designated AI, BI, CI, DI, EI, andF1 and the corresponding output terminals for the outbound cycleselector OCS are designated A0, B0, C0, D0, E0 and F0. Input circuitsare connected from these terminals 'to the operating coils of relays inthe oiiset selec-- tor individual to each of these circuits. These inputcircuits are connected to one side of the coil for each of the relaysIA, IB, IC, ID, IE, and IF respectively from the respective outputterminals AI through FI of the inbound cycle selector ICS. Inputcircuits for the relays 0A, OB, 00, OD, OE, and OF in the offsetselector OCS are similarly connected from the respective outputterminals AO through F0 of the outbound cycle selector OCS. The otherside of the coils of all of these relays are connected via wire l2 tothe A. C. negative lead at the left side of the figure.

During the trafiic sampling period timed by the common timer CST each ofthe cycle selectors rests in one of its several cycle positions inaccordance with 'a count of the traffic actuations of its associatedtraflic detector, and near the end of the traffic sampling perioddetermines whether it will step up to the next higher cycle in theseries from A to F or remain on the same cycle or step down to the nextlower cycle for the next trafiic sampling time period.

Each of the cycle selectors connects A. C. power to the one of itsoutput circuits and terminals corresponding to the cycle position it isthen selecting and maintains power on this output terminal until theshift is made to another output terminal near the end of one of thetrafiic sampling time periods.

For purpose of illustration in Fig. 2, it is assumed that the inboundcycle selector ICS is in its cycle position C and the outbound cycleselector is in its cycle position E for example, and A. C. plus powerwill thus be provided over circuits CI and E0 and relays IC and OE inthe offset selector will be energized and the remaining relays IA, IB,ID, IE and IF of the inbound group and 0A, OB, OC, OD, and OF oftheoutbound group will be. deenergized as shown in Fig. 3.

Each of these relays is provided with a group of contacts operated bythe associated coil and arranged in a vertical line below the coil witha broken line indicating the several contacts associated with theiroperating coil. When the coil of the relay is energized the severalarmatures of the contacts are pulled toward the coil away from thecontacts on the far side of the armature and toward the contacts on thenear side of the armature with respect to the coil, thus closing thelatter contacts and opening the contacts on the far side.

In the case of all the relays in this figure the contacts below thearmature, that is those on the far side of the armatures, are designatedwith even number reference numbers and are openedonly when the relay isenergizedand'such contacts will be referred to as break contacts'inaccordance with widespread practice of those skilled in the 'art.The'contactson the upper side of'thearmature, that is' those nearer therelay "coil, are closed only when the associated relay is energized,andwill be'referred'to as make contacts in accordance with widespreadpractice in the art. These latter make contacts are designated by oddnumber reference numbers in the figure. In some'cases, a common armatureis employedfor amake contact and a break contact, as shown for contactszb5 and its for example.

The relay IA is provided with the make contact ial and the break contact1128. IB is provided with the make contacts 1195, lb! andthebreakcontact 1725. The relay IC' is provided with the make contacts 2'05 andi! and the' breakcontact icG. The relay ID is'provided with the makecontacts-.idfidl and the break contact z'dfiu The. relay IE is providedwith" the make contacts'ie5; is? and the :break contact ie6. The

relay-IF is provided with the make contacts-1Y5, I if! thefbreak contactifli. The respectiverelays extend: to the right in the figure into theleft side of-a -cyclegenerator. indicated schematically 'bythe block'CG.Power is applied from the offset-selectorto the cycle generator overonlyone of these circuits at anyone timepcorre sponding'to the-highestcycle position assumed by -either of the cycle selectors ICS and 008 atthat time. For example, with relayICenergized-bycyc1e=selector-'ICSbeing in its 0- cycle positiom-andrelayOE energized by the cycle selector -OCsibeing 111- its cycle E positionas previously assumed;- then'power will be supplied from thepositivepower-wire at the'right of Fig;

3via-wire'- |3-, break-contact #6; wire 14, break contact ofG, wire l5,breakcontact ze6, wire 17,

make-contact 065;;Wire EGG to the'cycle'gener- H ator CG, thusenergizing this wire; While the other wires ACG, BCG, CCG, DCG; and FCGremain deenergized.

7 However if it is assumed for example that both of the cycle selectorsICS and 008 are in their A- cyclepositionthen relays IA and 0A only willbe energized in the inbound and out bound-groupsand-power will beapplied from the positive power wire-via wire 13, break contact- 276,wire |4;--break contact -0f6; wire l5, break contact ie6,;wire I],breakcontact oefi, wire l8; break contact id6; wire-; break contact odS;

Wire 2|, break-contact 1'05, wire 23, break contact Q65, wire-24, breakcontact z'bG, wire 26;

break contact obfiwo-wire-ACG to cycle generator 0G,;and the-remainin.WiresBCG, CCG, DSG ECG, and'FCG will be deenergized.

The abovegrouppf circuits-between the relay for the-circuitsACG throughFOG to-the cycle generator CG include the following. One cir+ cuitconnects contacts ib5 and ob5--inparallel via \vire28-to, WirE'BCG:Another ciruitcon nects contacts 'z'bfiwia'wire 26 to 'thecommonarmature of contacts obfi and 0125, and thecon The relay tact ob'E isconnected 'to' wi're' ACG. Another Cir cuit connects contact 1'05 -viawire 'to con'-' tact 005 and to \vir'eCCG. Another circuitconnectscontact iciivia Wire '23 to the' corninonarmature of contacts005 and -oc5, -the contact 006"being connected via wire 24 to thecommonarmature of contacts iZJS and ibB. Another circuit connects contact id5via wire 22 to contact 0% and to wire DOG. Another circuit connectscontact id-3 via wire 20 to the common armature of contaCtsodB and, od5andthe contact' odf is in turnconnected via wire 2! 'tothe' com'monarmature of the contacts ic5"and ic5.- Another circuit connects contactie5 via wire [9 to contact oe5 and to w'ir'eECG. Another circuitconnects contact ie6 viawire H to the common armature of contactsoe5"andoe5,

and the contact oefi isconnected via'wirelBto the'common armature ofcontacts idE and" id6. Another circuit connects contact U5 via wire I5to contact oj5 and to Wire FOG. Another circuit' connects the contactiffi via wire 14 to the common armatureofcontacts ojiiand offi, and"the'contact ofE is in turn connected via wire 15'- to "the commonarmature Of contacts z'e5and z'eBfi Another circuit connects plus powervia Wirel3 to the common armature of the contactsi/S Another group ofcircuits-employ the contact groups ial through if! and 0a! through ofl.

These circuits are associated with the selection ofthe inbound'oroutbound'ofis'et output circuits ICC andOCC' in accordance with therelative positions of the two cycle selectors ICS-and OCS asindicated bythe' closing of one'of the contaots-in the inbourid'and one ofthe'contacts in the 'outbound group just mentioned' This'se' lection ofthe offset circuits'is'accomplishedby' the selective operation of oneorthe othr'of thetwo relays IRJ-and OR shown tothe-left andright'of twotriode tube sections IV and OV shown having acommon tube envelope inthelower part of- Fig. 3. It will be obvious that these tube se'ctions'could be in separate envelopes" but I are 1 shown in the preferred'formwith a common envelope;

The re1a'yOR is in the anode circuitoi theinput "winding" TI-Il-Z. ofthe transformer TH connected via the wires "an'd' 3i to'the inbound andoutbound relay contact groups ial through ifTa'nd 0a? through 0f? and bythe group of circuitsfrom the armatures of these make contacts to' arons potentiometer formed by a series of resistors RI, R2, R3; R4,R5shown arrangedverticallyatthe middle of Fig: 3.

Theieft'side TH of the input winding of a the transformer TH isconnected Via wire 30 in matures comprising the lower sides of the-makecontacts of! andijl are connected in parallel viaw'ire 32 to theupper-end of resistor R1 and also via switch SW3 to the low voltage A:C.

power wire LV at the right sideof the figure. Wire 33 connects thearmature of contact oe'l with the common tap between resistors RI andR2.

' This common tap is also connected via wire 34 to the armature ofcontact iel. The armature of contact d! is connected via wire 35 to thetap between resistor R2 and resistor R3, this tap in turn beingconnected via wire 36 to the armature idl. The armature of contact 0c!is connected via wire 31 to the common tap between resistors R3 and R4,which tap is also connected via wire 38 to the armature of contact icl.The armature of contact ob'l is connected via wire 39 to the common tapbetween resistors R4 and RE, which tap is also connected via wire 4!! tothe armature of contact ibl. The armature of contact oa'i is connectedvia wire IiI to the lower end of resistor R5 which is also connected viawires 42 and 44 to the armature of contact ia'l. This lower end ofresistor R5 is the lower end of the potentiometer formed by theresistors RI to R5, and is also connected via wires 42 and 43 to thenegative power wire at the left of the figure. These resistors RI to R5are preferably of the same value and together in series provide apotentiometer between the A. C. power line LV at the right and thenegative A. C. power line at the left.

In the operation of the oiTset selector, one of the group of contactscal to of! will be closed in accordance with the cycle position in whichthe outbound cycle selector OCS is resting at any one time, and one ofthe group of contacts id? to if'l will be closed in accordance with thecycle position in which the inbound cycle selector ICS is resting at thesame time. Byvirtue of the closure of one of the outbound group of thesecontacts the right side of the input of transformer TH will be connectedvia wire 3i, via the closed contact to a particular tap on thepotentiometer provided by the resistors RI to R5. Corresponsingly theclosure of one of the inbound group of these contacts will connect theleft side of the input of transformer TH via wire 33 and the closedinbound contact to a particular tap on the potentiometer RI to R5.

For example if the cycle selector I08 is in the top cycle position F andthe cycle selector OC-S is in the bottom cycle position A then thecontact if"! will be closed and connect the left side of the input oftransformer Tl-I tothe upper end or" resistor RI, and the contact calwill be closed to connect the right side of input of transformer TH tothe lower end of resistor R5 so that the full low voltage A. C.potential between the positive side LV and the negative power wire willbe connected across the transformer TH input with the polarity such thatthe left side of this input winding will be connected to the A. C. powerline LV and the right side of the input winding will be connected to thenegative side of the A. C. power line.

However if for example the cycle selector- ICS is in its lowest cycleposition A and the cycle selector (JCS is in its top cycle position. Fthe conditions will be reversed and the left side of the input windingof transformer TH will be connected via closed contact id? to thenegative A. (3. power line at the lower end of resistor R5, and theright side of the input winding of the transformer TH will be connectedvia the closed contact of! to the A. C. power line LV and the upper endof resistor RI, thus connecting the full low voltage A. C. potentialacross the input winding 14 again but w'ithreverse polarity as comparedwith the condition previously recited.

If as originally assumed for illustration the cycle selectors ICS andOCS are in positions C and E respectively then contacts ic? and 0e! willbe closed as shown in Fig. 3, and the left side of input winding THI-Zwill be connected via wire 30, contact 2'01 and wire 38 to the tapbetween resistors R3 and R4, and the right side of input winding TIII2will be connected via wire 3!, contact oeI, wire 33, to the tap betweenresistors RI and R2.

It will be clear from an inspection of the circuit arrangementsdescribed for the contact groups id! to if! and call to of! and thepotentiometer RI to R5 that if the cycle selectors ICS and'OCS are inthe same cycle positions both ends of the input winding of transformerTH will be connected to the same tap on the potentiometer RI-RE andthere will be no A. C. power supplied to this input winding, but to theextent that either of the cycle selectors 108 or OCS is above the otherin its scale of cycle positions A to F its particular end of thetransformer input winding will be connected to a higher A. C. powerpotential than the other end, and the farther apart the cycle selectorsare on their corresponding scales of cycle positions the higher will bethe A. C. potential difference applied to the input winding, so thatboth the polarity and the potential difference applied to this inputwinding are determined by the relative positions of the two cycleselectors.

The control effect just described on the input winding of transformer THis employed to control the triode sections IV and 0V through theirrespective control grids, by connection of the latter to theoutputwinding TH35 of the transformer TH, so that neither of the anodecircuits of these triode sections are conducting if no potentialdiiference is applied to the input winding THI-2 or if only a ver lowpotential is applied to this winding as in the case of the two cycleselectors I08 and 008 bein in substantially corresponding cyclepositions. However one or the other of the anode circuits of 7 thesetriode sections will be made conducting by the efiect of the transformerTH on the respective control grids by sufiicient potential diiferen enceapplied to the input winding TI-II-2 and in accordance with the polarityof this potential difierence. For example, if the inbound cycle;selector ICS is substantially higher in the scale.- of cycle positionsthan the outbound cycle selector OCS, the polarity and potentialdifference applied to the input winding THI--2 will be such as tooperate in conjunction with the polarity and magnitude of the cathode toground and anode to ground voltages on triode sections IV and 0V so asto make the anode circuit of IV conducting and the anode circuit of 0Vnonconducting. On the other hand if cycle selector 00s is in a'substantially higher scale position than cycle selector ICS thepotential and polarity applied to the input winding THl-2 will bereversed to make triode OV conducting and triode IV nonconducting.

The grid control of the triode sections IV and 0V is provided byconnection with the output winding TH35 of transformer TH, the middle ofthis output winding at TH i bein connected via wire 46 to the negativeA. C. power line. The left end TH3 of this output winding is connectedvia resistor R8, wire 4! and resistor R6 to the control grid of thetriode section IV. The

right end TH5 of this output winding is connected via resistor R9, wire48,resistor R1 to the control grid of the triode section OV.

The anode circuits of triodes IV and V are connected to the positiveside of: the A. C.:line via the respective coils IR and OR and'wire 52.The cathodes of these sections are connected to potentiometer Pl toobtain-fromthe low voltage A. C. circuit L-V a cathode supply potentialhaving the same polarity as the A. C. positive line and of magnitude asdetermined by potentiometer Pl. When the potential across winding THl--2is zero or some low value, the. grids are set negative relative to thecathodes to such an extent as to have both triode sectionsIV and 0V in anon-conducting state when-wire'52, is positive with respect to ground.Both triode sections will be non-conducting when wire 52 is negativewith respect to ground.

The polarity andmagnitude of the voltage applied to transformer windingTHI-2 determines the polarity and magnitude of the grid voltage appliedto the two triodes with respect to ground. The Voltages applied to thetwo gridsare 180 degrees out of phase and therefore only one section canbecome conducting with any given applied voltage to the primary oftransformer 'I.H|2. One section will have a negative potential appliedto the grid with respect to ground in additionto the. positive.potentialbetween the cathode and ground during the time that the anode voltage ispositive with respect to ground and therefore remains non-conducting.As-v a result of .a-positivergridvoltage of sufiicientmagnitude withrespect to ground toovercome: theeffect: of the positive cathode.potentialiwith-respect to ground in theiother section this other sectionwill -become conducting": since-the A. C. potentialv applied to theanode is positive during this time;

The magnitude of thevoltage; across winding THl-2.r.equired' to makeoneofthe triodesiconducting is determinedlby the magnitude ofthevoltage:on:both'cathodes asset by:potentiometer P-l. One end of this;potentiometer is; connected to.A-. 0'. negative: power via wire. and theother. end is connected via wire 5| to. AC; power wireLV.

Thus the number: of. cycle; positions separation= betweenthe two' cycleselectors vICS and OCS'ZIB- quiredto make. one of" thetriodesconducting; is. adjustable :by meansofpotentiometer PILSO that: the;selection of one or the other. of the twoanode. circuits: of the triode.sections IV: and 0V to select one or theother Ofl the twodirectional'ofiset output circuits: can be: ma'dezto depend on a relatively small.difiference in: traffic: in the 'two directionsor on' a relativelyvlargeidifferencerasi desired by the traffic... authorities. Thustheselection of a preferential offset? for one/directioncan be made todepend on.the offsettselector for that direction being one or two', ormore positions aboveithe cycle. selector: for the other: direction.

Also' as will be. more 'fully" described' below this adjustmentdetermines the extent: to which the" intermediate or average offset ismaintainedfor somedegreeof separation of: the cycle selectors on theirscale of cycle. positions since in one preferred arrangement accordingto .the inven-- tion: if neither: inbound. nor outbound oil'set is"selected, as byf'both ;.of:'the.aanode circuits of" the triodesectionsrIV andOV being non-conductingthen the intermediateoraverageoffsetiis selected. This latter. selection; of the i average offset: may

ii G

16 be made 'for the; cycle selectors I08 and OCS beingat ornear the samecycleposition over the whole scale from A to F, ormay be made only wheneither cycle selector is higher than cycle position A, as desired. Inthe latter form of the invention a fourth ofisetor free independentoperation for. example. may be provided by both of" the cycle. selectorsbeing in the lowest cycle position A, but the intermediate or averageof!- .set provided with the cycle selectors in substantiallycorresponding cycle positions higher than A.

The-selection of preferential offset for one or theaother' direction orof average oiTset, in arc-- cordance with the degree of. separation ofthe two cycle selectors-in their scales'of cycle-positions has just beendescribed with switch SW2 in its. closed positionas. shown in Fig. 3.

If switch SW2 is'in its open position the de gree of separation or thetwo cycle selectors required to change from average to preferentialoffset can be made greater than the degree required to maintain suchpreferential offset against change back to average offset. Thisbiasing-action is sometimes desirable to increase the stability of thesystem of offset selection against too frequent shift of oifset underrapidly varying traffic conditions for example.

This biasing action is obtained by means of the adjustablepotent ometerP2 in cooperation with potentiometer PI and the contacts of the relaysIR and OR, as will be morefully described below.

With this biasing control, if two cycle positions separation is'requiredto select initially the outcontrolled by'adjustment of the relativepositions by the two potentiometer PI and P2; With the outbound offsetselected for example the potentiometer P! can be adjusted to determinethe number of positions separation betweenthe cycle selectors forshifting back to average offset. Then having made that shift the numberof positions necessary to shift again to outbound offset for example canbe determined by adjusting. of the potentiometer P2 and thereby agreater-separation can thus be provided for initial shift to apreferential offset than is required to maintain such preferentialoffset.

This biasing action i obtained with the switch SW2 open to makeeffective-the following circuits shown in the lower part of Fig. 3. Theright side of the potentiometer P-i! is connected via wire to the lowvoltage A. C. power LV. The right side of the potentiometer P2 is alsoconnected via wire 94 to the armature of make contact or? of relay OR,and via wire Sito the armature of the make contact ir'l of relay 1R.Potentiometer P2 as shownserves as a variable resistance.

The variable arm of potentiometer P2 is connected via wire 96 and wire89 to wire 32, which in turn is connected to the upper end of iepotentiometer ilk-R5. This arm of potentiometer PZis also connected viawire 5" wire 9i to=the make contact OH, and also via wire Thus wheneither 92 to the make contact irl.

17 of these make contacts is closed by the energization of theassociated relay IR or OR, the potentiometer P2 will 'be shunted and theA. C. voltage applied to potentiometer Rl-.-R5 will be reater than withboth contacts ir'! and or! open.

Under the condition of either relay IR or OR,

energized; the potentiometer Pl can be used to set the degree ofseparation of the two cycle selectors that will just maintain thepreferential offset. At a smaller degree of separation the offsetselector will return to average offset, under which condition relays ORand IR will both be deenergized, thereby opening the shunting ofpotentiometer P2 by either contact or? 'or ir'l. The total voltageacross potentiometer Rl-RS is now less than the condition wherepotentiometer P2 was shunted, the amount of reduction of voltagedepending upon the amount of resistance of potentiometer P2 included inthe circuit. With this reduced voltage operating in potentiometer Rl--R5the degree of separation of the two cycle selectors which will besufficient to cause either of the relays OR or IR to become energizedagain and select a preferential offset, will be greater.

The selection of the offsets by actuation of the respective outputcircuits ICC and OCC is accomplished by operation of the respectiverelays IR and OR, which are connected in the anode circuits of therespective triodes IV and 0V, the circuits ICC and OCC being controlledby contacts on these relays. The circuit OCC is connected through abreak contact ir4 of relay IR. When this break contact ir4 is closed, aswhen relay IR is deenergized, the circuit OCC is connected via contactirl, and Wire 6| to the break contact ia8 of relay IA, and is alsoconnected via wire 61 and wire 62 to the break contact oa8 of relay OA.When cycle selector ICS a is in any cycle position other than cycleposition A the break contact ia8 will be closed and connect positivepower via wire 63, wire 64, contact 118 to wire BI, and when cycleselector OCS is in any cycle position other than its cycle position A,then contact oa8 will be closed and positive power will be connected viawire 63, contact 0a8, Wire 62 to wire Bl. Thus if either cycle selectoris off of its cycle position A, then wire 6| will have positive powerand will supply this positive power over either one or both of thecontacts 11 or 014 if either one or both of these contacts is closed.

If cycle selector ICS is in a sufficiently higher cycle position thancycle selector OCS, then relay IR will be energized and relay OR will bedeenergized. Thus contact ir4 will be open and contact 0T4 will beclosed, and the positive power previously described as applied underthis condition to wire Bl will also be applied via wire 65 and theclosed contact 0T4 to the output offset circuit ICC. Under thiscondition the contact 1'1'4 will be open so that the output ofl'setcircuit OCC will be disconnected from the positive power on wire 6|.

If on the other hand cycle selector OCS is in a sufiiciently highercycle position than cycle selector ICS, then relay OR will be energizedand relay IR will be deenergized, and in this latter condition theoutput offset circuit OCC will be energized by the closed contact 11'4from the positive power on wire 6! as previously described and theoutput offset circuit ICC will be deenergized because of the opencontact 0T4.

If the offset selectors 108 and OCS are not sufficiently far apart incycle positions however to energize either relay IR'or OR in the anodecircuits of triode IV and 0V, then with both of these relays deenergizedboth contacts z'r4 and 0T4 will be closed and if either cycle selectoris off of its lowest cycle A position, one of the contacts M8 and outwill be closed as previously described and positive A. C. power will beapplied to wire BI and via contacts 2'14 and 0rd to energize both outputcircuits OCC and ICC.

In the event that it is desired to employ the condition ofdeenergization of both of the output circuits OCC and ICC as a controlfor free operation of the individual controllers or for a fourth offsetof a type different from the other three offsets for outbound traiiic,inbound traffic and average traffic for example, the positioning of bothcycle selectors ICS and OCS in the A cycle position will open bothcontacts 13:18 and 0a., and thus disconnect wire 6| from the A. C.positive power on wire 63, and with switch SWI in the open positionshown in Fig. 3 no A. C. positive power will be supplied to either ofcontacts ir l or 074 and A. C. power will therefore be disconnectedfrom. the output circuits OCC and ICC even though both of the relays IRand OR are deenergized with both cycle selectors ICS and OCS in positionA.

If it is desired however to provide thesame average cycle offset withboth cycle selectors in position A as with both cycle selectors in anyone of the other cycle positions the switch SW1 can be closed and thusconnect positive power 'via switch SW! and wire 66 to contact OM and viawire 65 to contact ir l so that both output circuits OCC and ICC will beenergized even with is sufficient so that for any number of positions ofseparation of the cycle selectors required for a preferential offsetselection the change of separation to such number of positions from oneless number will produce a change at the grid of one of the triodes toswitch that triode from nonconducting to conducting condition.

To limit the grid current drawn by the conducting triode in the event ofa large voltage on transformer TH, due to the cycle selectors beingseveral positions apart for example, or due to operation of relay SD,the resistors R6 and R1 are employed in the grid circuits of triodes IVand OV respectively.

Resistor R8 between wire 41 and transformer terminal TH3, and resistorRQ-between wire 48 and 'transformer te'rminal THE, limit the currentthrough transformer TH and the current from the power supply LV whenrelay SD is operated.

In order to improve the operation of relays IR and OR on the A. C. powerpositive excursions the capacitors IK and OK are preferably connectedacross the coils of relays IR and OR respectively.

At the lower left in Fig. 3 a relay SD is shown which is providedjwithmake contacts sdt, $115, $611, sdS, and sdl l. The right side of thecoil of relaySD is connected via wire 52 to the A. C. positive powerwire and the left side of this coil is connected via wire- 53 to outputcircuits in parallel from the two cycle selectors 1055 and 00S. As willmore fully appear by reference to Fig. 4 each of these output circuitsconnects wire 53 with a make contact on a relay SC in its associatedcycle selector. Each cycle selector 19 as disclosed in theaforementioned Patent 2,288,601 incorporates a relay SC which isenergized only during the stepping down operation of that cycleselector.

For the purpose of the present invention where a cycle selector isemployed of the type having a cyclic switch which has a six step scaleof cycle positions and is stepped forward rapidly five positions inorder to produce the equivalent of stepping backward one position, asdescribed in the Patent 2,288,601, an additional make contact ispreferably provided in each cycle selector on its relay SC. This makecontact, which is designated 303, will supply negative A. C. power viawire 53 to the left side of the coil of relay SI) and thus energizerelay SD when either one or both of the cycle selectors ICE; and OCS isstepping down.

An alternate arrangement for energizing relay SD may be employed byconnecting the wire 53 to the input circuits providing the step downpulse from the common cycle selector sampling period timer CST to therespective cycle selectors ICS and OCS. This alternate arrangement willavoid the provision of additional contacts on the cycle selector relaysSC but will cause the energization of relay SD at each actuation of thestep down pulse circuit from this common timer CST whether or not eitherof the cycle selectors is actually stepping down at that time.

With either of these alternate methods of energizing relay SD thepurpose of so energizing relay SD is to control circuits to maintain theoffset selection in its proper condition during any stepping downoperation of the cycle selectors where the cycle selector is of the typethat has a six step scale of cycle positions and steps forward rapidlyfive steps in order to step down one step for example. It will beobvious under such conditions that the cycle selector stepping down willstep successively through all of the intervening positions and thus mayenergize momentarily in sequence the several relays of the IA to IF orOA to OF groups. Since this action would produce artificial transcientconditions of difierent combinations of cycle positions for the twocycle selectors and corresponding conditions of potential and polarityon the transformer TH and on the control grids of triodes IV and 0V aspreviously described, it is desirable to provide for maintaining thetriodes IV and 0V and their respective relays IR and OR, in whatevercondition they were at the beginning of this stepping down operation. Inother words, during the stepping down operation of either of the cycleselectors, in order to avoid any transient effects the relays IR and OR.are maintained in the same condition as at the beginning of the steppingdown operation by the operation of relay SD and its contacts incooperation with the contacts 21'5- and M5 of relay IR, and the contacts0T5 and orfi of relay OR as will now be described.

Assume for example that both cycle selectors ICS and OCS have been incycle position C and C position the relays IR and OR will both bedeenergized and will thus have their make contacts 21'5 and 075 open andbreak contacts W6 and 075 closed respectively. Therefore under theseconditions negative A. C. power will be supplied via wire H, makecontact sdl 1, break contact ir5, and wire 12 to resistor R8 and to wire41 and resistor R6 to maintain a sufficiently low or substantiallyground grid potential on the triode section IV to maintain its anodecircuit nonconducting and maintain relay IR deenergized throughout thestepdown operation during which the relay SD is energized. Also underthese conditions negative A. C. power is supplied via wire '18, makecontact sd'l, wire 53, break contact orfi, wire M to resistor R9 and towire 48 and resistor R1, to apply a sufficiently low or substantiallyground grid potential to the triode section OV to maintain its anodecircuit at a very low conduction or substantially nonconducting level soas to keep the relay OR deenergized during the step down operation.

It will now be assumed for example that the cycle selectors ICS and OCSare in cycle positions E and C respectively at the beginning of thestepdown. operation of either of the cycle selectors and that relay IRis energized and relay OR deenergized. Then as soon as relay SD isenergized at the beginning of the stepdown operation low voltagepositive A. C. from wire LV for example will be applied via wire 75 andwire 16, via wire 11, make contact sdB, via make contact 1'1'5, wire 12,wire 41 to resistor R5 for the grid of triode section, IV to apply asufiiciently positive potential on the grid to maintain the triodesection IV conducting for energization of its anode circuit despite anyopposite potentials supplied to the transformer TI-I by the transientseparations of the cycle selectors With respect to their cycle positionsduring the step down operation of either one. Under the conditions justassumed with cycle selectors ICS and OCS in positions E; and Crespectively, relay OR. is maintained deenergized during stepdownoperation by the circuit previously described over make contact sdl andbreak contact 0T6 to maintain substantially ground or low grid potentialon triode section IV.

If it is now assumed that the cycle selectors ICS and OCS are in cyclepositions C and E respectively for example, with relay IR deenergizedand relay OR energized as shown in Fig. 3, immediately before the startof step-down operation of either cycle selector, then relay OR will bemaintained energized, during the stepdown operation, by the followingcircuit. Low voltage A. C. positive power is applied from wire LV viawire '15, wire 76, make contact sd5, wire 18, make contact 0T5, wire '14and wire d8 through resistor Rl to the grid of triode section OV so asto maintain a sufficiently high positive voltage on this control grid tomaintain the triode section OV conducting to hold relay OR energizedduring the step-down operation. Relay IR is maintained deenergized underthe present assumed conditions by the previously described circuitsupplying negative A. C. power via wire il, make contact sdll, breakcontact irfi, wire 72 and wire 4'! through resistor R6 to the controlgrid of triode section IV.

Thus as descibed above the relays IR and OR are maintained in whatevercondition of ener gization of either one energized or both deenergizedthese relays had immediately prior to the beginning of the step-downoperation. This is controlled by the relay SD to maintain this holdingcondition throughout the step-down operation and then release it so thatat the end of the stepdown operation the relays IR and OR. assumewhatever condition of energiza-tion and deenergization is needed tocorrespond with the new steady state positions of the cycle selectorsICS and OCS.

It will be appreciated that if a cycle selector employing a reversiblestepping switch is used instead of a cycle selector which steps forwardfive steps in order to step down one step in a repeated scale of sixpositions, then the relay SD and its associated circuits via thecontacts ir5,

z'rfi, 0T5 and 015 will not be necessary, since in this case thestep-down will be directly from one cycle position to the next lowercycle position without intervening transient conditions. 1

In this connection a further protective circuit is provided inconnection with step-down operation by the make contact sd3 of relay SDin order to connect positive A. 0. power via wire 8! and contact sd3 towires BI and 65 so as to maintain A. C. power to contacts ir4 and 0Mduring stepdown operation of one of the cycle selectors while the otheris resting in the cycle A position. This auxiliary supply of A. 0. powerto contacts ir4 and 0M under this condition will maintain the powersupplied to either or both of the circuits OCC-and ICC in accordancewith the opened or closed condition of the respective .contacts ir l and074 corresponding to the energized or deenergized conditions of theirassociated relays IR and OR at the beginnin of the step-down oper ation.It will be appreciated that if one of the 1 cycle selectors happens tobe resting in its .cycle A position while the other cycle selectorhappens to be stepping down by stepping ahead five steps from oneintermediate cycle position to another intermediate lower cycle positionthe second cycle selector will momentarily pass through its cycle Aposition in such step-down operation and this would momentarilydisconnect the power supply via the contacts 2'11 and 0M for the circuitICC to OCC unless this auxiliary power supply via wire 8! and contactsd3 were provided at this time.

It will also be appreciated that this circuit via contact sd3 and wire8| could also be eliminated if a reversible type of stepping switch isemployed in the cycle selectors so the step-down operation could be madedirectly down one step instead of by stepping up one less step than thetotal number of steps in a repeated scale of positions, as previouslydescribed.

Referring now to Fig. 4 there is shown the circuit and cam diagram forthe common sampling period timer CST employed for the two cycleselectors ICS and OCS. These cycle selectors are indicated at the leftand right of Fig. 4, and enough of the external connecting wires areindicated schematically in Fig. 4 as in Fig. 1 and Fig. 3 to correlatethese units of the master control apparatus as shown in the severalfigures.

As in the previously mentioned Patent 2,288,601 relating to a singlecycle selector employing a single sampling period timer, the presentcommcn sampling period timer CST employs a continuously operating motorM and the cams S, T, and R- operated by this motor, as shown inside theblock designated CST in Fig. 4. These cams open and close periodicallythe respective contacts SI, TI and RI, in a traffic sampling period timecycle as indicated by the cam contour and the accompanying cam chartshowing by the present invention, which employs two cycle selectors, theadditional cam contacts S2, T2 and R2 are provided, to be operated bythe cams S, T, and B respectively at the same times as contacts Si, Tiand RI, and these added contacts S2, T2 and R2 are connectedrespectively to the wires extending to the right into the outbound cycleselector OCS, these wires being designated 0-16, 0-, and 0-19respectively to correspond with the wires 76, i4 and T9 of the cycleselector circuit of Patent 2,288,601 as previously mentioned.

One side of the motor is connected to A. C. positive power via wire I!and the other side of the motor and the cam following members of all thecam contacts are connected to negative A. C. power via wire It, so thatnegative power is applied to the wires to both cycle selectors when theassociated cam contacts are closed, but these circuits are separatedfrom each other when the associated cam contacts are open.

As more fully described in the above mentioned Patent 2,288,601 thesampling period timer may provide a sampling time period ofapproximately six minutes by one revolution of its cams for example, andduring this sampling time period it maintains contacts TI and T2 closedexcept at the end of the period at which time the contacts are openedbriefly to release a counting limit relay in connection with reset ofthe traffic counting to start a new sampling period. The cam s closesits contacts SI and S2 very briefly at a point somewhat before the endof the sampling time period to pctentialize the cycle selectors to stepup to the next higher cycle position if suificient traffic has beencounted at that time. The cam R closes its contacts RI and R2 just priorto the end of the sampling time period to potentialize the cycleselectors to step down to the next lower cycle position if insufficienttraffic has been counted at this time. The cam R and its contacts RI andR2 also serve to reset the traffic counting for the succeeding samplingtime period. Although both cycle selectors are potentialized to step upor down as just described, each cycle selector steps up or down orremains unchanged in accordance with its own trafiic countingindependent of the other.

The relay contact SCfi shown in the cycle Se 'lectors in Fig. 4 areconnected to wire 53, which extends to one side of the coil of relay SDin Fig. 3 to operate the latter as previously described. The relaycontacts SCB are make contacts and are associated with the coils of therelay SC shown in phantom in the two cycle selectors ICS and OCS. Therelay SC is energized briefly when its associated cycle selector isstepping down to a lower cycle position.

Referring now to Fig. 5 a circuit arrangement for one form of the cyclegenerator CG is shown, employing a series A. C. motor designated M andassociated A. C. generator driven by the motor M. The speed of the motorM and generator GN is varied by the several circuits ACG, BCG, CCG, DCG;ECG, FCG connected by adjustable taps on the potentiometer P3 shown. inthe left side of the block CG. This potentiometer P3 provides resistancein series with the motor circuit, the amount of such resistance beingvaried in accordance with the particular one of the several cir cuitsACG through FCG energized from A. C. positive power through theoperation of the offset selector OS as described in connection with Fig.3. The offset selector will energize only one of these circuits at atime from A. C. power in accordance with the highest position assumed atthat time by either of the cycle selectors ICS or OCS. The A. C. powerthus applied via one of these circuits will extend from the associatedtap on the potentiometer P3 through the upper part of the potentiometerP3 to the left side of the motor M. the right side of this motor beingconnected to negative A. C. power. Thus the speed of the motor will bevaried and the speed of the generator will be correspondingly variedthis wire will supply this A. C. power to a relatively high resistancepoint on the potentiometer P3 in Fig. 5 to drive the motor relativelyslowly in the cycle generator CG so that a relatively low frequencyoutput will be suppleid on the wires VCC-l and VCC2 from the generatorGN.

Referring now to Fig. 6 two representative intersections along thehighway HY are again shown, together with the master control wiresextending along the highway. providing the variable cycle power circuitVCC[ and VCC-2 and the oifset control circuit 000 and ICC, as well asthe resynchronizing circuit RSC as previously described. In addition inFig. 6 however one form of the circuit of the local cycle-offset controlunit is shown. The circuit is shown for each of two local control units[LC and ZLC, illustrating that the circuits may be the same although thepositions of the cam or other suitable devices for providing theindividual offsets for the individual traflic controllers may bedifferent at different intersections.

Thus the circuit and cam arrangement for the local cycle offset unit !LCis shown at the left of Fig. 6 and the circuit and cam arrangement forthe unit 2L0 is shown at the right. The two cam arrangements illustratetwodifferent sets of ofisets for the two traffic controllers [TC and ZTCfor the respective signals ITS and ZTS, as will be noted from thedifferent positions illustrated for the respective sets of cams.

Referring now to the circuit for the local offset unit [LC at the leftof Fig. 6, three relays are shown EBR, [AR and IRS, the designation ofthe relay being applied to the coil and the associated contact beingindicated by a broken line extending from the coils to the armatures ofthe contacts as previously described and illustrated in connection withFig. 3. To the right of the relays a motor driven group-of cams CR, ICA,[C1, and [C0 are shown, and to. the left of these cams a.

-,-group of cam contacts, operated by the respective cams, are shown anddesignated ISR, ISL [S2 and [$3.

The several cams are rotated by the synchronous motor [M which isenergized preferably via an amplifier [AM from the variable cycle leadsVCC-[ and VCC-2 to which it is connected as shown. The right side of theoutput of the am plifier is continuously connected to the coil of themotor [M and the left side of the amplifier output is connected toground, and is completed to the motor coil via a break contact [m4 ofrelay IRS, and a cam contact [SR connected in parallel by wire [24,either of which contacts may complete the circuit over a wire i23 to themotor coil. The motor [M is operated at a slow or fast rate a desired inaccordance with the relatively low or relatively high frequency power onthe variable frequency power circuit VCC-[ and VCC-2, so long as eithercam contact [SR or relay contact lrs i is closed.

Resynchronization is provided once per cycle by the cooperative actionof these contacts with relay IRS being under control of the mastercontrol unit MCU of Fig. 1 and Fig. 8. The latter unit contains aresynchronization control cam MCR. For best continuity of service camMCR is shaped to open its contact MSR for a slightly longer period thanthe local unit cams [CR and ZCR for example. The internal apparatus andwiring of the master control unit MCU is shown in Fig. 8.

The master control resynchronization cam MCR will close its associatedcontacts MSR throughout all but a small part of its cycle and open thesecontacts briefly for this small part of its cycle. The notched portionof cam [CR shown at the left of the cam is illustrative of the part ofthe cycle during which the contacts [SR are opened. Thus it wil beunderstood that the cams [CR and 2GB of Fig. 6 will be rotating insynchronism with the similar cam MCR in Fig. 8. When cam MCR opens itscontacts positive power will be disconnected from the resynchronizingwire RSC common to the several intersections along the highway HY. Thisdeenergization of wire RSC will deenergize relays IRS and ZRS as shownin Fig. 6, thus closing the break contacts [rs4 and 21's4 to completethe left side of the coil circuits from the motors [M and 2Mrespectively to their respective amplifiers.

Thus if by reason of a momentary power failure or some other factor themotor [M and its associated cam group were to fall behind the mastercontrol unit MCU, the cam [CR would open its contacts [SR at the end ofits cycle in the approximate positon shown in Fig. 6, and if it issufliciently behind the master control cam MCR the. latter will. alreadyhave reenergized wire RSC and relay [RS and thus already have opened thecontacts [1'84 so that the motor [M will be disconnected from power andstop until the master control unit completes its cycle to reopencontacts MSR and deenergize wire RSC. At such time, with thedeenergization of the wire RSC and relay [-RS, power will be reappliedto the motor [M via the break contacts lrs4, and the cam [CR and theassociated cams below will be restarted in synchronism with the mastercontrol unit again.

On the other hand if the local control unit [LC should by anycircumstance be ahead of the master control unit MCU then as soon a thecam [CR reaches the approximate position shown in Fig. 6 in its cycle itwill stop the motor [M by 25" opening the contacts ISR,--sinceitis'assumed that the corresponding cam in the -master control unit hasnot yet openedv its associated cam contacts at this time to deenergizewire- RSC and thus the contact Irs4 is open. The motor IM will thusremain at rest until the master control cam MCI-t reaches a positioncorresponding with ICR, at which time the cam MCR will open itscontacts, deenergize RSC and relay IRS to reconnect power to the motorIM via contacts Irsd as previously described, and the local unit ILCwill then proceed through its cycle in synchronism with its mastercontrol unit MCU.

The relays IBR and 'IAR in the local cycle offset unit ILC, are providedwith contacts as follows. Relay IBR has the make contact Ibr3 and thebreak contact Ibr4 operated by a common armature. The relay IAR has themake contact Iar3 and the break contact Iar l operated by a commonarmature, and the make contact Iar5 and the break contact Ia'rB operatedby a common armature.

The offset control circuits for the offset cam contacts ISI, ISZ and IS3are connected to be placed into operation by the contacts of relays IBRand IAR in accordance with the actuation of the circuits ICC and OCC bywhich these relays are controlled in accordance with the selection ofoffset by the offset selector 05 as described in connection with Fig. 3.

Thus with the circuit ICC deenergized and the circuit OCC energized asillustrated in Fig. 3 for the assumed condition of the inbound cycleselector in its cycle position C and the outbound cycle selector in itscycle position the relay IBR will be deenergized and the relay IAR willbe energized as illustrated in Fig. 6. Under this condition ground or A.C. negative power will be applied via break contact Ibr4', wire I2 I,make contact Ian-5, wire 00C to cam contact I83. The remaining circuitsAOC and IOC to the cam contacts ISI and ISZ will be disconnected fromnegative power because of open contacts Ibr3 and Ian-4 respectively.Also the wire FRC will be disconnected from the A. C. negative powerbecause of the open contact IarB. Thus the only one of these fourcircuits receiving negative power via the contacts'of relays IBRand'IAR; is the circuit OCC, connected with the cam contacts IS3. Thesecontacts IS3 are opened and closed cyclically in accordance with thecontour of cam ICO which is determined as desired for the outboundoffset for the associated traffic controller ITC and its traffic signalITS. With the circuit conditions with the outbound circuit OCC onlyenergized as just described the cam contacts IS3 will cyclically app'ynegative power for brief periods via wire IPC to the traffic controllerITC, under control of the outbound ofiset cam ICOO. If it is assumedhowever that the offset selector OS is selecting an inbound offset inresponse to heavier inbound traffic, then the circuit ICC will beenergized and the circuit OCC deenergized; Under these latter conditionsthe relay IBR will be energized and the relay IAR will be deenergized.Then the relay contact 'Ibr4 will be open, thus disconnecting A. C;negative or grounded power from the wire 000 as Well as the wire FRC,and relay contact lbr3 will be closed, thus connecting this power viathe wire I22 and break contact Iar-I to wire IOC and cam contacts ISZwhich are under the control of the inbound cam ICI. With make contactIar3 open under these conditions thewire ADC is also disconnected fromthe negative power and thus theinbound ofiset set cam 26' cam'contactsIS2 are the only ones effective to connect negative power to the trafficcontroller ITC via the wire IPC, thus making only theinbound offseteffective for this controller.

If it is now assumed however that the average or intermediate offset isbeing selected by the offset selector due to substantially balancedtraffic actuations in opposite directions along the highway HY, thenboth wires OCC and ICC will be energized and both relays IBR and IARwill be energized. Under these assumed conditions negative power will besupplied via make contact Ibr3, wire I22 and make contact Iar3 to wireA00 and the cam contact ISI operated by the average off- ICA. Sincebreak contacts Ibr4 and lard are open under the latter assumedconditions the other circuits IOC, OCC and PEG can not supply thenegative power to wire IPC; and the wire AOC is the only one which cansupply negative power via cam contacts ISI and wire IPC to trafIiccontroller ITC so that the latter is controlled on the average offset bythe cam ICA.

If it is assumed however that both wires OCC and ICC are deenergized, asfor example by selection of free offset operation in accordance withboth cycle selectors 10s and OCS being in their cycle A positions, thenboth relays IBR and IAR will be deenergized, and the wire FRC will besupplied with negative power via break contact Ibr l, wire I2I and breakcontact Iarfi. Wire FRC thus supplies negative power directly andcontinuously via wire IPC to the traffic controller ITC under theseconditions and the cam contacts ISI, ISZ, I53 are obviously ineffectiveto control wire IPC.

Thus in accordance with the selection of the oifset control circuits OCCand ICC by the offset selector in response to a determination of thetime rates of trafiic actuation in the respective directions alonghighway HY, each local cycle offset unit will provide appropriate offsetcontrol to its local trafiic controller by means of an offset controlcam in the local cycle offset unit which is maintained in synchronismwith the master control unit; and in the event of extremely lighttraffic conditions or any interruption of power on both circuits OCC andICC, each local cycle offset unit will provide free or independentoperation of the local traffic controller. It will be appreciated thatthe circuit for the local cycle offset units 2L0, 3LC and the like arethe same as described for the unit ILC, except for the relay and contactdesignations which are coded for the respective units as indicated inFig. 6 for 2L0.

Referring now to Fig. '7 the circuit of one form of traffic controllerITC is illustrated schematically. This circuit is primarily that of asimple form of a traffic actuated controller but is provided with aswitch SWF which can be closed to convert the controller from trafiicactuated to fixed time operation if desired, and thus serves toillustrate both forms of operation under control of the several offsetsystems via the wire IPC shown entering the lower part of the rectangleITC.

The controller ITC as illustrated in Fig. 7 is provided with asynchronous motor TM and a series of cams rotated by this motor. Threecams TCS, TCR and TCM are shown in Fig. 7. The

cam T08 is illustrative of one of a group of cams ordinarily provided ina traffic controller unit for operating the several signal circuits ofthe traffic signal ITS providing preferably the usual green, yellow andred signals for the respective intersecting streets. Since the camcontrolled operation of such signal circuits is already well-known asdisclosed in the Patent 2,279,896 of H. A. Wilcox for example, only oneof such cams is illustrated in Fig. 8 as TCS to correlate the positionsof the other cams TCR and TCM with respect to the high way green signalperiod, the cam TCS controlling the cam contacts TS-I shown at the rightof the cam to control the highway green signal of the trafiic Signal ITSvia wire 'III]. The cam TCS is shown near the end of the highway greensignal period with positive A. C. power connected via the cam contactsTS-I and the wire I I to the traflic signal ITS.

The cams TCM and TCR control the operation of the motor TM driving theseveral cams under control of relay IRD and the wire IPC on the localcycle offset unit ILC of the master control apparatus. The motor TM ispreferably of the synchronous type and has the left side of its coilconnected to A. C. positive power, and the right side of its coilconnected via wire II I and wire I I 2 to the junction H3 connectedbetween the relay contact H113 and the cam contact TS-3. The latter camcontact is controlled by the cam TCM which, as indicated by its contour,opens the cam contact TS-3 near the end of the highway green periodprovided by cam TCS. With the cam contacts TS3 open as shown the motoris able to receive negative power for operation only via the relaycontact Ird3 or the switch SWF from the wire IPC from the local cycleoffset unit ILC. If traffic actuated operation of the controller I TC isassumed, the switch SWF will be open as shown in Fig. 7, and thus themotor TM will receive negative power for its operation in the positionshown only via the relay contact Ird3. This relay contact is controlledby the relay IRD which in turn is controlled by the traflic actuateddetector switches lDSi and IDSZ which are shown connected in parallel.These are the detector switches which are located in the side streetapproaches to the intersection controlled by the signal ITS and thecontroller ITC.

The left side of the coil IRD is connected to positive power and theright side of this coil is connected via wire TM, and either of thedetector switches IDSI or IDSZ to negative power if one of the latterswitches is closed by trafiic actuation. Momentary closure of one of thelatter switches by traflic actuation by a vehicle approaching on theside road for example will momentarily energize the relay IRD byapplying negative power to the right side of its coil via wire H4. Inthe position of the cams shown, after such initial actuation, the relayIRD will be maintained energized via wire H5 and its make contact I rd5and the cam contact TS-2 to negative power, the latter cam contact beingcontrolled by the cam TCR and being closed at this time.

Energization of relay IRD as described will close its contact Ird3, andwith the cam positions as shown near the end of the highway greenperiod, will connect the right side of the motor TM via wire III, wire'II2, junction 'II3, relay make contact IrdB to wire IPC. The wire IPCwill have negative (grounded) A. C. power applied to it via one of thecam contacts ISI, ISZ, or IS3 of the local cycle offset unit ILC,depending upon which offset is operative as selected by the offsetselector as previously described in connection with Fig. 3, unless freeoperation is being selected by the offset selector, in which latter casethe wire FRO in the local cycle offset unit ILC will supply negativepower continuously over circuit IPC.

Assuming for example that the outbound offset is being selected with thecycle selectors ICS and OCS in their positions C and E respectively aspreviously described, them the cam ICO in Fig. 6 will periodically closeits contact [S3 for a brief period once per cycle and connect the A. C.negative or grounded power for this brief period via wire IPC to thecontroller ITC. This brief period is sometimes referred to as thepermissive period for the controller ITC, and the application of powerfor the permissive period is referred to as the permissive pulse, thispulse being provided by whichever of the offset circuits AOC, IOC, 00Cor FRC is operated in connection with the selection of ofisets by theoffset selector.

Thus when the permissive pulse of negative power is provided on the wireI PC and the relay IRD is energized in the traffic controller ITC bytrafiic actuation for example, this negative power supplied by thepermissive pulse on wire IPC is connected via contact Ird3, and wires 1I2 and III, to the motor TM to start the motor. The operation of themotor rotates the cams TCM, TCR, and TCS in a clockwise direction asshown to start these cams through one trafiic control cycle for thesignal ITS. The cam TCS deenergized the wire "H0 to disconnect thehighway green signal and the cams of the controller ITC continue throughtheir cycle providing a side street green period and then a highwaygreen period before returning to rest in the position shown in Fig. 7near the end of the highway green period. During this cycle of operationthe cam TCR opens its contacts TS-2 during the side street green periodand deenergizes the relay IRD, thus reopening the contacts Ird3 and Ird5and preparing the relay for subsequent trafiic actuation.

The motor TM is operated initially from its rest position shown in Fig.7 via the contact M113 and wire IPC as previously described, but as soonas cam TCM has rotated out of the rest position shown it will close itscontacts TS-3 and apply negative power via wire H2 and III to maintainthe motor TM operating throughout the remainder of the traflic signalcycle until the cam TCM reaches again its rest position shown, at whichtime the motor will be stopped by the reopening of the cam contact TS3unless there has been a subsequent traffic actuation of reenergize relayIRD and the permissive negative power is again available on wire IPC.

The operation of the controller ITC as a fixed time or non-trailicactuated controller is illustrated for example if the switch SWF isclosed in Fig. '7, whichwill connect the permissive pulse wire I PCdirectly to the motor TM via the wire II I. It will be obvious that thepermissive pulse via wire IPC must be of sufiicient length to enable themotor TM to drive the cam TCM out of the rest position and reclose itscontacts TS3.

It will be appreciated that the motor TM may be operated if desired fromthe variable frequency power Wires VCC-I and VCC-Z via an amplifiersimilar .to the amplifier IAM of Fig. 6 for example to automaticallyvary the time cycle of the cams TCS, TCR and TCM and the correspondingtime cycle of the trafiic signal ITS in accordance with the shorter andlonger time cycles provided from the cycle generator CG in the mastercontrol apparatus of Fig. 1 and Fig. 3. In this form of operation theleft side of the motor TM is connected to the right side of theamplifier instead of directly to positive A. C. power.

It will be appreciated that the trafiic controller cams may be operatedstep-by-step by a ratchet their associated cam contacts if desired, inthe local cycle offset unit ILC.

Although a cycle generator of a type employing a variable speedmotor-generator is illustrated in Fig. 5 it will be appreciated by thoseskilled in the art that an electronic variable frequency generator maybe used if desired, such as the familiar audio frequency generatoremployed in electrical laboratories, in the cycle generator in place ofthe motor-generator unit shown.

Although a number of alternate forms of arrangements of apparatusaccording to the invention have been pointed out above it will beobvious to those skilled in the art that other modifications of theapparatus or in the arrangement or character of its parts may be madewithout departing from the spirit of the invention.

I claim:

1. In a trafiic control system, preferential offset control circuitsindividual to each of two direc-.

tions along a roadway, means for counting trafiic per unit timeindividually in each of such directions, and means for actuating thecontrol circuit for either direction in response to measurement of asubstantially higher rate of traffic per unit time for that direction ascompared with the other direction.

2. In a traffic control system, preferential offset control circuitmeans individual to eachof two directions along a roadway,non-preferential offset control circuit means for traffic in both ofsuch directions, means for counting traffic per unit time individuallyin each of such directions, means for actuating the preferential offsetcircuit means for either one direction alone in response to measurementof a substantially higher rate of traffic per unit time for such onedirection, and'nieans for actuating the non-preferential offset circuitmeans in response to measurement of substantially the same rate oftrafiic per unit time in both directions.

3. A structure as in claim 2, and including means-controlled byactuation of one alone of said preferential offset circuit means to biassaid circuit actuating means to maintain such one circuit means actuatedfor a smaller differential traffic ratethan that for actuating itinitially.

4. In a traffic controlsystem having two preferential offset systems,one for each of two opposite directions along a roadway, the combinationof trafiic actuated means individual to each of such directions, meansfor measuring the time rate of trafiic actuations of the respectivetraffic actuated means, and means controlled by said measuring means forselecting the preferential offset system for whichever direction has apredominating rate of traffic actuations, and time controlled means forperiodically resetting said measuring means.

5. In a traffic control system having a cycle selector and associatedtraffic actuated means for each of two traffic directions along aroadway, each such cycle selector having a multiplicity of outputcircuits representing a scale of cycle positions any one of which may beassumed'by the cycle selector corresponding to a time rate of trafi'icactuations of its associated trafi'ic actuated means, an offset selectorapparatus having input circuits for connection to the output circuitsfor the respective cycle selectors to be actuated thereby in accordancewith the positions assumed by said cycle selectors, said offset selectorapparatus also including output circuits for preferential offset systemsfor the respective traffic directions, and means forming a part of saidoffset selector apparatus to actuate the one output circuit forwhichever direction has a materially higher scale input circuitactuated.

6. A structure as in claim 5, and including means for predetermining atmore than one the number of positions of separation of said cycleselectors for such selection of one preferential offset.

7. A structure as in claim 5 and including means for providing anadjustable degree of separation of the positions assumed by the twocycle selectors for selection of either one preferential offset.

8. A structure as in claim 5, and including a multiplicity of outputcircuits from said offset selector apparatus corresponding to the scaleof cycle positions of the cycle selectors and meansfor actuating onlyone of said last named output circuits at a time in accordance with thehighest cycle position assumed at such time by either of the cycleselectors.

9. A structure as in claim 5, and including a multiplicity of outputcircuits for providing a selection of cycle lengths over a scalecorresponding to the cycle positions of such cycle selectors, and meansforming a part of said offset selector apparatus to actuate only one ofsaid last named output circuits at a time corresponding to the highestcycle position assumed at such time by either of the cycle selectors.

10. A structure as in claim 5, and including output circuit means for anoffset system for traffic in both directions and means forming a part ofsaid offset selector apparatus to actuate the last named output circuitmeans in response to actuation of input circuits for substantially thesame cycle positions for the two cycle selectors except for both of saidcycle selectors being in their lowest position on their scale ofpositions, and additional output circuit means for a system of offsetcontrol to permit individual trafiic signal controllers to run throughtheir cycles independently, and means for actuating said additionaloutput circuit in response to actuation of input circuits for the lowestcycle position for both cycle selectors.

11. A structure as in claim 5, and including output circuit means for anoffset system for traffic in both directions and means forming a part ofsaid offset selector apparatus to actuate the last named output circuitmeans in response to actuation of input circuits for substantially thesame cycle positions for the two cycle selectors.

l2. Selector apparatus for traffic control systerns, including inputcircuit means actuatable to represent a scale of low to high trafficflow rates for one traffic direction, second input circuit meansactuatable to represent a substantially similar scale of low to hightrafiic flow rates for -a second traffic direction, output circuit meansfor a control system favoring trai'lic in the first direction, secondoutput circuit means for a control system favoring trafiic in the seconddirec tion, and third output circuit means for a con-,

trol system providing for substantiallybalanced traffic movement in bothdirections, and means 31 interconnecting said 'input circuit 'means withsaid output circuit means to actuate -said first output circuitmeansalone in response to actuat-ion-of l said 'first 2 input circuit meansat a substantially-higher trafficflow'rate'thansaid secon'd inputcircuit' means and to actuate-"the secondoutputcircuit means alone-inresponse "to actuation of-sa-id second input-means at asubstant-iallyhighertraific-flow rate-than said first input circuitmeans, and said interconnecting means 'also in'cluding meansto' actuatesaid third output circuit means in response to actuation of the firstand second input circuitmeans at substantially thesame'tr-affic flowrate.

13. Selectorapparatuses-in claim 12 and in which-said interconnectingcircuit means includes an impedance element the impedance of which iscontrolle'd by said input circuit means in-accordance- -withthe relativepositions 'of saidinput circuit means'ont'heir respective scales of-traffic flow rates, and an impedance responsive'device controlled bysaid impedance element tO-SWitOh among 'said several output circuitmeans as aforesaid.

14.:Selector apparatus as inclaim l2 andin which said interconnectingcircuit means includes -;a ipotentiometerelementcorresponding to thescalesofitraffic rate offlow of said input circuit means, "a .potentialresponsive element differentially responsive to predeterminedpotential'of opposite :.po1arity, and connecting means controlled -tbyi'the respective input circuit 'means to connect'potential fromvarious vpoints on said potentiometer tozsaid potential-responsive ele-111E111; ntoapply a.'potentialdiiference to the latter .oftdegreecharacteristiciof theidegree of sepa ration of .the respective inputcircuit 1 means as actuated .-.alongtheirrrespective scales of :trailicrate of flow and of polarity characteristic of the higher TOf thetwo'input circuitrm'eans on the scale iofitraflic lfiow rate.

15.;In an offset selector apparatus, :a multiplicity of input :circuitsincluding corresponding :groups for each rof two trafiic directions andrepresenting substantially corresponding .scales :of-trafficfiow values,,output circuit means:pro viding l. for traffic signal system oiisets'individual to'the two directionsiand an intermediate offset forlei-directional traffic, sand selector means forming a partof saidapparatus for receiving actuations from the respective input circuitgroupsto actuate the output circuit for azdirectional offset in responsetozactuatio-n of a materially higher scale input circuit for thecorresponding direction group than for-theother direction group, andmeans forminga part of said selector -means for actuating the'intermediate output circuit means .in response .to actuation of inputcircuits of substantially-the same scale position for the twodirections.

"16. In an offset selector apparatus as inclaim 15, said selectormeansincluding a series of impedance elements connected to provide ar-multi--tap,.potentiometer, a potential responsive element differentiallyresponsive to potential ofrdifierent .polarity, connections between therespective input-circuits and said taps, and-means actuated bysaid.potential.-responsive element to actuate said output circuits inresponse to'the actuation of the :respective input circuits.

17..:In; an: offset, selector apparatus as. iniclaim 15;;said selectormeans includlng'a seriesof imipedanceelements connected to .provide a-mu1t-i- :tap potentiometer between "A. .0 power and ground terminalsa-transformerwhaving input and output windings, switch means individualto and controlled-by the respective input circuits for the respectivedirections and including one switch for-each 'direction'for eachposition on the scale cftraificflow values and operable in response toactuation of its controlling input circuit to connect thecorrespondingtapon the potentiometer to the input winding of saidtransformer, the switches ior-onetraific direction connecting to one endof said input winding and the switches for the second traffic directionconnecting to'the opposite end of said inputwinding, a connection from acenter-tap'on said output winding to ground-two' triodo tube-sections,connections between one-endof=saidoutput winding and the grindofone-said section and'between-the other end-of said output-winding andthe gridof said other'section, connections'between the cathodes of bothsections and-an A. C. potential intermediate said power and groundterminals, and anode circuits'in'dividual to the tWo-triode sections andcontrolledby the respective grids to actuate one-anode circuit only inresponse to connection toasubstantially higher scale potentiometer tapfor the'first direction than for the second direction and to'actuate'theotheranode circuit only in response to connection to asubstantially'higher scale potentiometer tap for the second direction than for thefirst direction, whereby neither of said anode circuits will be actuatedin response to connection to substantially the same scale tap on thepotentiometer for-two directions, and means for actuating the respectiveoutput circuits for the respective directions in responseto actuation ofthe respective anode circuits and for actuating the intermediate output-circuit in.response"to non-actuation of both .isaidnanode. circuits.

ZISUInH-a selector apparatus responsive to the relative positions'ofxtwocycle selectors each having .a scaleof cycle positions which it assumesone'at a'time for a;trafiic sampling'time period in :accor'dancewithtrafiicsampled in a different one .ofztwotrafficzrdirectionsin apreceding such 'timezperiod, .aljfirst group of relay and input circuits:for "actuation of said relays individually insresponsetoithe positionassumed by afirst of saidracycleselectors,asecond group of relays andinputccircuits 'foractuaticnof said latter relays individually inresponseitot the positionassumed tby'the :second of said cycleselectors, contact means'form-ingarpartzof the, respective relays to:be:operatedbyractuation thereof, a series of impedance; elementsconnected between A. 0., power and: return terminals to provide apotentiometer witha multiplicityiof taps,-a transformer having input andoutput windings, a pluralit of circuits connecting-oneend of said inputwinding to therespectivetapson said'potentiometer, each circuitincluding one of said contactmeans closed by.-actuation .oiitsassociated relay of the'first group-another pluralityof circuitsconnecting the otherendiof saidzinput winding with said respective taps,andeach including'one of'said contact means closed byiactuation of itsassociated relayofthe second group, aconnection'frcm the oenterof'thecutput winding'to said A. C. return terminal, two triode tubesections, a connection fromea potential intermediate saidvA. C."powereandrreturn terminalsto the cathodes of .both said :zsections,anode circuits individual :to the :two' tube sections,v connectionsbetween the respective ends:of :the output winding and the controlrgridstof .the :respezitive-sections for actuating onei'anodecircuit;in'response:to;a.pre-

